Lung cancer is the leading cause of cancer deaths in men and women both in the United States (Jemal A, Simard E P, Dorell C, et al Annual Report to the Nation on the Status of Cancer, 1975-2009, Featuring the Burden and Trends in Human Papillomavirus (HPV)-Associated Cancers and HPV Vaccination Coverage Levels. J Natl Cancer Inst 2013; Jemal A, Bray F, Center M M, Ferlay J, Ward E, Forman D. Global cancer statistics. CA Cancer J Clin 2011; 61:69-90) and worldwide (Boyle P L B, ed. The World Cancer Report 2008. Lyon, France: IARC; 2008). Survival rates remain dismal, with 5-year survival ranging from <5% for distant, to 24% for regional, to 53% for localized disease (Horner M, Ries L A G, Krapcho M, et al. SEER Cancer Statistics Review, 1975-2006. In. Bethesda, Md.: National Cancer Institute; 2009). This substantial survival rate decrease in advanced disease provides a strong motivation to search for early diagnostic and prognostic biomarkers.
Current clinically accepted methods for the early detection of lung cancer are limited to spiral CT scanning in smokers between the ages of 55 to 74 and a 30 pack year smoking history (Jaklitsch M T, Jacobson F L, Austin J H, et al. The American Association for Thoracic Surgery guidelines for lung cancer screening using low-dose computed tomography scans for lung cancer survivors and other high-risk groups. J Thorac Cardiovasc Surg 2012; 144:33-8; American Cancer Society. American Cancer Society Guidelines for the Early Detection of Cancer, 2013. However, spiral CT scanning provides a high rate of false positives, namely 96.4% overall and 24% of those with invasive testing (Aberle D R, Adams A M, Berg C D, et al. Reduced lung-cancer mortality with low-dose computed tomographic screening. N Engl J Med 2011; 365:395-409). Also, spiral CT scanning may lead to an attendant increase in lung cancer risk due to radiation exposure (Brenner D J. Radiation risks potentially associated with low-dose CT screening of adult smokers for lung cancer. Radiology 2004; 231:440-5; Buls N, de Mey J, Covens P, Stadnik T. Health screening with CT: prospective assessment of radiation dose and associated detriment. JBR-BTR 2005; 88:12-6). Thus, a concordant biomarker to better identify those who should be screened or undergo invasive diagnostic work-ups is needed. Importantly, while imaging techniques perform poorly in identifying early stage lung cancer, the use of molecular biomarkers provides hope for early detection. However, to date, no molecular biomarker for early stage lung cancer has been validated (Vansteenkiste J, Dooms C, Mascaux C, Nackaerts K. Screening and early detection of lung cancer. Ann Oncol 2012; 23 Suppl 10:x320-7; Hassanein M, Callison J C, Callaway-Lane C, Aldrich M C, Grogan E L, Massion P P. The state of molecular biomarkers for the early detection of lung cancer. Cancer Prev Res (Phila) 2012; 5:992-1006).
Several biomarkers are available for the assessment of overall prognosis and for guiding therapy. For example, the KRAS mutation in non-small cell lung cancer (NSCLC) confers a significantly shorter survival (HR=1.21) in stage IV disease (Johnson M L, Sima C S, Chaft J, et al. Association of KRAS and EGFR mutations with survival in patients with advanced lung adenocarcinomas. Cancer 2013; 119:356-62). The presence of an ALK or EGFR mutation indicates a responsive tumor to targeted therapies and longer survival (Lynch T J, Bell D W, Sordella R, et al. Activating mutations in the epidermal growth factor receptor underlying responsiveness of non-small-cell lung cancer to gefitinib. N Engl J Med 2004; 350:2129-39; Paez J G, Janne P A, Lee J C, et al. EGFR mutations in lung cancer: correlation with clinical response to gefitinib therapy. Science 2004; 304:1497-500; Pao W, Miller V, Zakowski M, et al. EGF receptor gene mutations are common in lung cancers from “never smokers” and are associated with sensitivity of tumors to gefitinib and erlotinib. Proc Natl Acad Sci USA 2004; 101:13306-11; Mok T S, Wu Y L, Thongprasert S, et al. Gefitinib or carboplatin-paclitaxel in pulmonary adenocarcinoma. N Engl J Med 2009; 361:947-57; Antoniu S A. Crizotinib for EML4-ALK positive lung adenocarcinoma: a hope for the advanced disease? Evaluation of Kwak E L, Bang Y J, Camidge D R, et al. Anaplastic lymphoma kinase inhibition in non-small-cell lung cancer. N Engl J Med 2010; 363(18):1693-703. Expert Opin Ther Targets 2011; 15:351-3). However, current clinically accepted biomarkers for lung cancer outcomes are based on tumor assays, an invasive approach that can be limited due to tissue availability.
Urine is gaining increasing interest as a biospecimen for detecting cancer biomarkers (Schmidt C. Urine biomarkers may someday detect even distant tumors. J Natl Cancer Inst 2009; 101:8-10), notably because it is collected noninvasively, abundant, and requires minimal preparation. Presently, only one urinary cancer biomarker is clinically applied, PCA3, for detecting prostate cancer (Groskopf J, Aubin S M, Deras I L, et al. APTIMA PCA3 molecular urine test: development of a method to aid in the diagnosis of prostate cancer. Clin Chem 2006; 52:1089-95). However, no clinically applied biomarkers exist for lung cancer, but promising urinary biomarkers include modified nucleosides (Henneges C, Bullinger D, Fux R, et al. Prediction of breast cancer by profiling of urinary RNA metabolites using Support Vector Machine-based feature selection. BMC Cancer 2009; 9:104; Hsu W Y, Chen W T, Lin W D, et al. Analysis of urinary nucleosides as potential tumor markers in human colorectal cancer by high performance liquid chromatography/electrospray ionization tandem mass spectrometry. Clin Chim Acta 2009; 402:31-7; Jeng L B, Lo W Y, Hsu W Y, et al. Analysis of urinary nucleosides as helper tumor markers in hepatocellular carcinoma diagnosis. Rapid Commun Mass Spectrom 2009; 23:1543-9; Manjula S, Aroor A R, Raja A, Rao S, Rao A. Urinary excretion of pseudouridine in patients with brain tumours. Acta Oncol 1993; 32:311-4; Sasco A J, Rey F, Reynaud C, Bobin J Y, Clavel M, Niveleau A. Breast cancer prognostic significance of some modified urinary nucleosides. Cancer Lett 1996; 108:157-62; Vreken P, Tavenier P. Urinary excretion of six modified nucleosides by patients with breast carcinoma Ann Clin Biochem 1987; 24 (Pt 6):598-603; Xu G, Di Stefano C, Liebich H M, Zhang Y, Lu P. Reversed-phase high-performance liquid chromatographic investigation of urinary normal and modified nucleosides of cancer patients. J Chromatogr B Biomed Sci Appl 1999; 732:307-13; Xu G, Schmid H R, Lu X, Liebich H M, Lu P. Excretion pattern investigation of urinary normal and modified nucleosides of breast cancer patients by RP-HPLC and factor analysis method. Biomed Chromatogr 2000; 14:459-63), where high levels indicate an increased RNA turnover and degradation. Clinical trials evaluating the utility of these nucleotides in various diseases, including cancer, are ongoing.
Metabolomics is an increasingly popular approach for uncovering new biomarkers for diagnosis (Kim Y S, Maruvada P, Milner J A. Metabolomics in biomarker discovery: future uses for cancer prevention. Future Oncol 2008; 4:93-102; Kind T, Tolstikov V, Fiehn O, Weiss R H. A comprehensive urinary metabolomic approach for identifying kidney cancerr. Anal Biochem 2007; 363:185-95; Matsumura K, Opiekun M, Oka H, et al. Urinary volatile compounds as biomarkers for lung cancer: a proof of principle study using odor signatures in mouse models of lung cancer. PLoS One 2010; 5:e8819; Sreekumar A, Poisson L M, Rajendiran T M, et al. Metabolomic profiles delineate potential role for sarcosine in prostate cancer progression. Nature 2009; 457:910-4; Yang Q, Shi X, Wang Y, et al. Urinary metabonomic study of lung cancer by a fully automatic hyphenated hydrophilic interaction/RPLC-MS system. J Sep Sci 2010; 33:1495-503; Yuan J M, Gao Y T, Murphy S E, et al. Urinary levels of cigarette smoke constituent metabolites are prospectively associated with lung cancer development in smokers. Cancer Res 2011; 71:6749-57) and customized treatment (Fan T W, Lane A N, Higashi R M. The promise of metabolomics in cancer molecular therapeutics. Curr Opin Mol Ther 2004; 6:584-92), and for evaluating characteristics of metastatic cells (Mountford C E, Wright L C, Holmes K T, Mackinnon W B, Gregory P, Fox R M. High-resolution proton nuclear magnetic resonance analysis of metastatic cancer cells. Science 1984; 226:1415-8) and carcinogenic tobacco-smoke constituents (Church T R, Anderson K E, Caporaso N E, et al. A prospectively measured serum biomarker for a tobacco-specific carcinogen and lung cancer in smokers. Cancer Epidemiol Biomarkers Prev 2009; 18:260-6; Hecht S S, Hatsukami D K, Bonilla L E, Hochalter J B. Quantitation of 4-oxo-4-(3-pyridyl)butanoic acid and enantiomers of 4-hydroxy-4-(3-pyridyl)butanoic acid in human urine: A substantial pathway of nicotine metabolism. Chem Res Toxicol 1999; 12:172-9; Hecht S S, Murphy S E, Stepanov I, Nelson H H, Yuan J M. Tobacco smoke biomarkers and cancer risk among male smokers in the Shanghai Cohort Study. Cancer Lett 201). However, most studies suffer from limited sample sizes, quality control, and lack of technical and biological validation. Metabolomic studies are unique and powerful because they measure both exogenous (e.g. cigarette smoke constituents) and endogenous molecules from cellular processes reacting to different types of exposures. Among methods for measuring metabolites, mass spectrometry is very sensitive and requires only small quantities of biospecimens (Griffin J L. The Cinderella story of metabolic profiling: does metabolomics get to go to the functional genomics ball? Philos Trans R Soc Lond B Biol Sci 2006; 361:147-61). A recent study has provided proof of principle evidence for the use of metabolomics in smokers that demonstrates the reliability and reproducibility of the assay, and the ability to distinguish levels and smoking status (Hsu P C, Zhou B, Zhao Y, et al. Feasibility of identifying the tobacco-related global metabolome in blood by UPLC-QTOF-MS. J Proteome Res 2012).